This application relates to a freeze dryer and, more particularly, to a corrosion-proof freeze drying assembly.
In general, the freeze drying techniques of the prior art provided only the removal of water from a heat-sensitive sample. More recently, however, more and more materials desired to be freeze dried contain corrosive acidic and basic substances. Researchers have continued to use standard freeze dryers for these materials, with resulting corrosion to condensers, chamber and vacuum pumps and heavy repair charges on replacing inaccessible condensers, refrigeration systems and pumps.
Thus, in view of the growing use of exotic chemicals having unknown properties, the need for a truly chemically resistant, totally serviceable freeze dryer has become apparent to researchers. Only when a researcher can perform any freeze drying technique on any material he chooses without undue concern for that material's ability to corrode will the true capabilities of freeze drying be realized.
Certain plastic materials have long been known for their chemically resistant properties. However, until the present invention, certain difficulties have been encountered when attempting to use these plastics to advantage in freeze drying applications. To rigidly support the plastic chamber, welding techniques have been tried, without success, since the weld would expand and contract at different rates than the plastic of the chamber and crack, destroying the weld. In addition, the chamber itself would not have sufficient strength to withstand the high vacuums in use.